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Abstract:

The abstract has been amended as follows: A method of dispensing a
hardenable dental composition, which can form a temporary bond,
comprising 1) providing multi-part hardenable dental composition
comprising part (A) in the form of a paste comprising acid-reactive glass
particles and a liquid selected from the group consisting of water, a
monomer having at least one ethylenically 10 unsaturated group per
monomer molecule, and a combination thereof; and part (B) comprising a
water soluble polyacid and a liquid selected from the group consisting of
water, a monomer having at least one ethylenically unsaturated group per
monomer molecule, and a combination thereof; and 2) extruding the
composition through a static mixer in fluid communication with a first
reservoir containing the part (A) and a second reservoir 20 containing
the part (B); wherein a plunger is positioned in each reservoir for
simultaneously forcing part (A) and part (B) into the static mixer.

Claims:

1. A method of dispensing a hardenable dental composition, which can form
a temporary bond, comprising: providing multi-part hardenable dental
composition comprising: part (A) in the form of a paste comprising:
acid-reactive glass particles and a liquid selected from the group
consisting of water, a monomer having at least one ethylenically
unsaturated group per monomer molecule, and a combination thereof; and
part (B) comprises: a water soluble polyacid and a liquid selected from
the group consisting of water, a monomer having at least one
ethylenically unsaturated group per monomer molecule, and a combination
thereof; wherein: an adhesion reducing component is included in part (A);
part (B); or parts (A) and (B); water is included in part (A); part (B);
or parts (A) and (B); the monomer having at least one ethylenically
unsaturated group per monomer molecule is included in part (A); part (B);
or parts (A) and (B); and at least one component for initiating
polymerization of the monomer is included in part (A); part (B); or parts
(A) and (B); extruding the composition through a static mixer in fluid
communication with a first reservoir containing the part (A) and a second
reservoir containing the part (B); wherein a plunger is positioned in
each reservoir for simultaneously forcing part (A) and part (B) into the
static mixer, extruding the composition through the static mixer, and
dispensing the composition; and wherein an extrusion force of less than
40 pound-force (178 newtons) according to Test Method I is applied to the
plunger for extruding the composition through the static mixer without
the aid of a mechanical advantage provided by an attached or external
device.

2. A method of bonding a prosthetic device to a dental structure
comprising: dispensing the hardenable dental composition according to
claim 1 onto a surface of a dental prosthetic device, a surface of a
dental structure, or a combination thereof; positioning the device on the
dental structure; and hardening the dental composition to form a bond,
which can be a temporary bond; wherein the prosthetic device is selected
from the group consisting of a crown, bridge, inlay, onlay, post,
abutment, veneer, and prosthetic tooth; and wherein the dental structure
is a prepared tooth or an implant.

3. A dental device comprising: a multi-part hardenable dental
composition, which can form a temporary bond, comprising: part (A) in the
form of a paste comprising: acid-reactive glass particles and a liquid
selected from the group consisting of water, a monomer having at least
one ethylenically unsaturated group per monomer molecule, and a
combination thereof; and part (B) comprises: a water soluble polyacid and
a liquid selected from the group consisting of water, a monomer having at
least one ethylenically unsaturated group per monomer molecule, and a
combination thereof; wherein: an adhesion reducing component is included
in part (A); part (B); or parts (A) and (B); water is included in part
(A); part (B); or parts (A) and (B); the monomer having at least one
ethylenically unsaturated group per monomer molecule is included in part
(A); part (B); or parts (A) and (B); and at least one component for
initiating polymerization of the monomer is included in part (A); part
(B); or parts (A) and (B); a first reservoir containing the part (A); a
second reservoir containing the part (B); a static mixer in fluid
communication with or which can be connected in fluid communication with
the first and second reservoirs; and a plunger positioned in each
reservoir for forcing part (A) and part (B) into the static mixer,
extruding the composition through the static mixer, and dispensing the
composition; wherein an extrusion force of less than 40 pound-force (178
newtons) according to Test Method I is required for extruding the
composition through the static mixer without the aid of an attached or
external device for providing a mechanical advantage.

4. A dental kit comprising the device of claim 3 and a plurality of
static mixers adapted for fluid communication with the first and second
reservoirs.

5. A multi-part hardenable dental composition, which can form a temporary
bond, comprising: part (A) in the form of a paste comprising:
acid-reactive glass particles and a liquid selected from the group
consisting of water, a monomer having at least one ethylenically
unsaturated group per monomer molecule, and a combination thereof; and
part (B) comprises: a water soluble polyacid and a liquid selected from
the group consisting of water, a monomer having at least one
ethylenically unsaturated group per monomer molecule, and a combination
thereof; wherein: an adhesion reducing component is included in part (A);
part (B); or parts (A) and (B); water is included in part (A); part (B);
or parts (A) and (B); the monomer having at least one ethylenically
unsaturated group per monomer molecule is included in part (A); part (B);
or parts (A) and (B); and at least one component for initiating
polymerization of the monomer is included in part (A); part (B); or parts
(A) and (B); wherein the composition can be extruded through a static
mixer in fluid communication with a first reservoir containing the part
(A) and a second reservoir containing the part (B); wherein a plunger is
positioned in each reservoir for simultaneously forcing part (A) and part
(B) into the static mixer and extruding the composition through the
static mixer; and wherein an extrusion force of less than 40 pound-force
(178 newtons) according to Test Method I is applied to the plunger for
extruding the composition through the static mixer without the aid of a
mechanical advantage provided by an attached or external device.

6. (canceled)

7. (canceled)

8. (canceled)

9. The method of claim 1, or the device of claim 3, wherein part B
further comprises a liquid monomer having at least two ethylenically
unsaturated groups per monomer molecule and having a viscosity less than
or equal to the viscosity of Bis-GMA.

10. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. (canceled)

15. (canceled)

16. The method of any one of claim 1, the device of claim 3, the kit of
any one of claim 4, or the composition of claim 5, wherein part (A), part
(B), or part (A) and part (B) further include a nonreactive filler in an
amount of 1 to 50 weight percent based upon the total weight of the part
which includes the nonreactive filler.

17. (canceled)

18. (canceled)

19. (canceled)

20. (canceled)

21. The method of claim 1, or the composition of claim 5, wherein the
water soluble liquid monomer is selected from the group consisting of
2-hydroxyethyl methacrylate, glycerol monomethacrylate, polyethylene
glycol dimethacrylate, sorbitol methacrylate, and a combination thereof.

22. The method of claim 1, or the composition of claim 5, wherein the
polyacid is of the formula: B(X)m(Y)n wherein B is a
hydrocarbon backbone, X is --COOH, Y is an ethylenically unsaturated
group, m is at least 2, n is at least 1, and Y is attached to B via an
amide linkage.

23. The method of claim 22, the device of claim 22, or the composition of
claim 22, wherein the polyacid is selected from the group consisting of
the reaction product of a polymer selected from the group consisting of
polyacrylic acids, copolymers of acrylic and itaconic acids, copolymers
of acrylic and maleic acids, copolymers of methyl vinyl ether and maleic
anhydride or maleic acid, copolymers of ethylene and maleic anhydride or
maleic acid, copolymers of styrene and maleic anhydride or maleic acid,
and a combination thereof with a coupling compound selected from the
group consisting of acryloyl chloride, methacryloyl chloride, vinyl
azalactone, allyl isocyanate, 2-hydroxyethyl methacrylate,
2-aminoethylmethacrylate, and 2-isocyanatoethyl methacrylate.

24. (canceled)

25. (canceled)

26. The method of claim 1, or the composition of claim 5, wherein the
acid-reactive glass is FAS glass.

27. The method of claim 1, or the composition claim 5, wherein the part
(A) and part (B) are in a volume ratio of 1.2:1 to 1:1.2.

28. (canceled)

29. The method of claim 1, or the composition of claim 5, wherein the
adhesion reducing component is selected from the group consisting of
polyethylene glycol, glycerol, water soluble or dispersible celluloses,
and a combination thereof.

30. (canceled)

31. (canceled)

32. (canceled)

Description:

BACKGROUND

[0001] Two-part glass ionomer cements have been in dental use for some
time. Such materials are comprised of an ionic polymer component and a
reactive glass component, which when mixed together in the presence of
water undergo a cement setting reaction. These dental materials provide
several desirable attributes including prolonged fluoride release,
tolerance to moisture and saliva, good mechanical properties and
excellent adhesion to dental hard tissues without pretreatments such as
conditioners or adhesives. Powder-liquid, powder-paste, paste-paste,
paste-liquid, and liquid-liquid two-part cements have been reported.
Traditionally, the two parts have been measured out in some way and hand
mixed or spatulated; although in one alternative a two-compartment
capsule with pre-measured powder and liquid components has been used with
vibratory mechanical mixing. Various drawbacks have become evident with
these materials and methods, including, for example, mechanical strength
variability, varying consistencies, unsatisfactory working or setting
times, cost per application, multiple dispensing and mixing steps,
mechanical mixing equipment and waste.

[0002] More recently, the use of auto mixing delivery systems for two
component paste/paste dental materials has addressed some of the above
limitations, providing some ease of use, time savings and consistent
product performance. In the case of glass ionomer cements, such systems
have included a device requiring the combination of a cartridge and a
device providing a significant mechanical advantage.

[0003] However, there continues to be a growing interest in alternative
methods and compositions for delivering glass ionomer cements and related
materials in a faster, easier and/or more simplified manner.

SUMMARY

[0004] It has now been found that certain multi-part hardenable glass
ionomer dental compositions for preparing temporary dental cements can be
dispensed through a static mixer by applying only hand pressure without
the aid of a mechanical advantage provided by an attached or external
device. The low force required for dispensing the compositions and small
size of a dispensing device that can be used with the compositions allow,
among other benefits, direct dispensing of the composition in the mouth.

[0005] Accordingly, in one embodiment, there is provided a method of
dispensing a hardenable dental composition, which can form a temporary
dental cement, comprising:

[0006] providing multi-part hardenable dental composition comprising:
[0007] part (A) in the form of a paste comprising: [0008] acid-reactive
glass particles and a liquid selected from the group consisting of water,
a monomer having at least one ethylenically unsaturated group per monomer
molecule, and a combination thereof; and [0009] part (B) comprises:
[0010] a water soluble polyacid and a liquid selected from the group
consisting of water, a monomer having at least one ethylenically
unsaturated group per monomer molecule, and a combination thereof;

[0011] wherein: [0012] an adhesion reducing component is included in
part (A); part (B); or parts (A) and (B); [0013] water is included in
part (A); part (B); or parts (A) and (B); [0014] the monomer having at
least one ethylenically unsaturated group per monomer molecule is
included in part (A); part (B); or parts (A) and (B); and [0015] at least
one component for initiating polymerization of the monomer is included in
part (A); part (B); or parts (A) and (B);

[0016] extruding the composition through a static mixer in fluid
communication with a first reservoir containing the part (A) and a second
reservoir containing the part (B);

[0017] wherein a plunger is positioned in each reservoir for
simultaneously forcing part (A) and part (B) into the static mixer,
extruding the composition through the static mixer, and dispensing the
composition; and

[0018] wherein an extrusion force of less than 40 pound-force (178
newtons) according to Test Method I is applied to the plunger for
extruding the composition through the static mixer without the aid of a
mechanical advantage provided by an attached or external device.

[0019] In another embodiment, there is provided a method of bonding a
prosthetic device to a dental structure comprising:

[0020] dispensing the hardenable dental composition according to claim 1
onto a surface of a dental prosthetic device, a surface of a dental
structure, or a combination thereof;

[0021] positioning the device on the dental structure; and

[0022] hardening the dental composition to form a temporary dental cement;

[0023] wherein the prosthetic device is selected from the group consisting
of a crown, bridge, inlay, onlay, post, abutment, veneer, and prosthetic
tooth; and

[0024] wherein the dental structure is a prepared tooth or an implant.

[0025] In another embodiment, there is provided a dental device
comprising:

[0026] a multi-part hardenable dental composition, which can form a
temporary dental cement, comprising: [0027] part (A) in the form of a
paste comprising: [0028] acid-reactive glass particles and a liquid
selected from the group consisting of water, a monomer having at least
one ethylenically unsaturated group per monomer molecule, and a
combination thereof; and [0029] part (B) comprises: [0030] a water
soluble polyacid and a liquid selected from the group consisting of
water, a monomer having at least one ethylenically unsaturated group per
monomer molecule, and a combination thereof;

[0031] wherein: [0032] an adhesion reducing component is included in
part (A); part (B); or parts (A) and (B); [0033] water is included in
part (A); part (B); or parts (A) and (B); [0034] the monomer having at
least one ethylenically unsaturated group per monomer molecule is
included in part (A); part (B); or parts (A) and (B); and [0035] at least
one component for initiating polymerization of the monomer is included in
part (A); part (B); or parts (A) and (B);

[0036] a first reservoir containing the part (A);

[0037] a second reservoir containing the part (B);

[0038] a static mixer in fluid communication with or which can be
connected in fluid communication with the first and second reservoirs;
and

[0039] a plunger positioned in each reservoir for forcing part (A) and
part (B) into the static mixer, extruding the composition through the
static mixer, and dispensing the composition;

[0040] wherein an extrusion force of less than 40 pound-force (178
newtons) according to Test Method I is required for extruding the
composition through the static mixer without the aid of an attached or
external device for providing a mechanical advantage.

[0041] In another embodiment, there is provided a dental kit comprising
the above device and a plurality of static mixers adapted for fluid
communication with the first and second reservoirs.

[0042] In another embodiment, there is provided a multi-part hardenable
dental composition comprising:

[0043] part (A) in the form of a paste comprising: [0044] acid-reactive
glass particles and a liquid selected from the group consisting of water,
a monomer having at least one ethylenically unsaturated group per monomer
molecule, and a combination thereof; and

[0045] part (B) comprises: [0046] a water soluble polyacid and a liquid
selected from the group consisting of water, a monomer having at least
one ethylenically unsaturated group per monomer molecule, and a
combination thereof;

[0047] wherein: [0048] an adhesion reducing component is included in
part (A); part (B); or parts (A) and (B); [0049] water is included in
part (A); part (B); or parts (A) and (B); [0050] the monomer having at
least one ethylenically unsaturated group per monomer molecule is
included in part (A); part (B); or parts (A) and (B); and [0051] at least
one component for initiating polymerization of the monomer is included in
part (A); part (B); or parts (A) and (B);

[0052] wherein the composition can form a temporary dental cement;

[0053] wherein the composition can be extruded through a static mixer in
fluid communication with a first reservoir containing the part (A) and a
second reservoir containing the part (B);

[0054] wherein a plunger is positioned in each reservoir for
simultaneously forcing part (A) and part (B) into the static mixer and
extruding the composition through the static mixer; and

[0055] wherein an extrusion force of less than 40 pound-force (178
newtons) according to Test Method I is applied to the plunger for
extruding the composition through the static mixer without the aid of a
mechanical advantage provided by an attached or external device.

Definitions

[0056] The term "temporary cement" refers to a cement which can hold a
dental material, such as a dental prosthetic device, for example, a
crown, in place on a dental structure, such as a prepared tooth or
implant, under normal oral conditions of use for the service life of the
device, and further, which facilitates easy removal of the device when
needed without damage to the tooth or implant. Such temporary cements,
therefore, allow easy removal, whether they are in use for a long period
of time, which may be considered permenant, or for a short period of
time, which may be considered temporary.

[0057] The term "temporary bond" refers to a bond formed by the temporary
cement to dentin and/or enamel, such that a dental material so bonded to
a dental structure can be removed easily without damage to the dental
structure, such as a tooth or an implant. The term "water soluble" refers
to a material, such as a monomer or polymer, which dissolves partially or
fully in water and dissolves in water alone in an amount of at least 5 g
per liter of water at 25° C., or which dissolves in water combined
with a monomer, a cosolvent, and/or a surfactant in an amount of at least
5 percent by weight at 25° C. The term "comprising" and variations
thereof (e.g., comprises, includes, etc.) do not have a limiting meaning
where these terms appear in the description and claims.

[0058] As used herein, "a," "an," "the," "at least one," and "one or more"
are used interchangeably, unless the context clearly dictates otherwise.

[0059] Also herein, the recitations of numerical ranges by endpoints
include all numbers subsumed within that range (e.g., the range of
viscosity ratios 1:0.06 to 1:13 includes 1:0.06 to 1:13, 1:0.1 to 1:13,
1:0.25 to 1:13, 1:0.5 to 1:13, 1:0.6 to 1:13, 1:1 to 1:13, 1:0.06 to
1:10, 1:0.06 to 1:7.5, 1:0.06 to 1:5, 1:0.06 to 1:3.5, 1:0.06 to 1:1,
1:0.1 to 1:10, 1:0.25 to 1:7.5, 1:0.5 to 1:5, 1:0.6 to 1:3.5, 1:0.75 to
1:2, 1:0.9 to 1:1.1, etc.).

[0060] The above summary of the present invention is not intended to
describe each disclosed embodiment or every implementation of the present
invention. The description that follows more particularly exemplifies
illustrative embodiments.

BRIEF DESCRIPTIONS OF THE FIGURE

[0061] FIG. 1 is a perspective view of an assembled dental device for
mixing and dispensing a multi-part hardenable dental composition as
described herein.

[0062] FIG. 2 is a perspective view of a static mixer included in the
assembled dental device of FIG. 1.

[0063] FIG. 3 is an exploded view in perspective of an alternative dental
device for mixing and dispensing a multi-part hardenable dental
composition as described herein.

[0064] FIG. 4 is a cross-sectional view of the device of FIG. 3 in
assembled form showing parts (A) and (B) in separate reservoirs prior to
being forced into the static mixer.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

[0065] As indicated above, previous methods for auto mixing glass ionomer
cements have included a device for providing a mechanical advantage.
Examples of such devices include dispensing guns and appliers such as GC
FujiCEM automix and Paste Pak Dispenser. This has been found to be
undesirable, for example, because of the significant bulk required for
the mechanical-advantaging device, making direct dispensing at a dental
structure in the mouth difficult and/or impractical. The methods,
devices, kits, and compositions presently provided allow effective static
mixing and dispensing of multi-part hardenable dental compositions, which
can be used for preparing temporary cements, using hand pressure without
mechanical-advantaging devices. As a result, the practitioner may now
conduct auto mixing of multi-part hardenable dental compositions,
including glass ionomer cements, using a small sized dispensing device
and without hand fatigue or exceptional hand strength.

[0066] The cements prepared using the methods, devices, compositions, and
kits described herein, in certain embodiments, have been found to provide
additional benefits, including ease of removing excess cement during
placement and fluoride ion release. At the same time a desirable balance
of retention and removal characteristics are achieved.

[0067] The methods, devices, compositions, and kits presently provided are
applicable to multi-dose and unit-dose applications. In multi-dose
applications, a replacement static mixer is used with each successive
application of the composition. The above kit embodiment, therefore,
includes a plurality of static mixers.

[0068] The above device described herein may be provided with a static
mixer in fluid communication with the first and second reservoirs or with
the static mixer not yet attached, but which can be connected in fluid
communication with the first and second reservoirs at an appropriate
time. FIG. 1 illustrates one example of an assembled dental device 100 in
the form of a double syringe for mixing and dispensing a multi-part
hardenable dental composition. Syringe body 101 includes reservoir 105,
containing one part of the composition, for example, part (A), and
reservoir 106, containing another part of the composition, for example,
part (B). Mixing tube 102 contains a static mixer (not shown) and is
equipped with optional curved dispensing tip 104. Alternatively, tube 102
may simple taper to a smaller diameter. Mixing tube 102 may be an
integral part of syringe body 101, for example, when a unit-dose
application is contemplated. Alternatively, mixing tube 102 may be
removable and replaceable, for example, when multi-dose applications are
to be carried out. Plunger 103 in device 100 is used to force parts (A)
and (B) into and through mixing tube 102. As described above, only hand
pressure is required to carry this out. It has now been found that an
extrusion force of less than 40 pound-force (178 newtons) according to
Test Method I described below meets this requirement. For certain
embodiments, preferably an extrusion force of not more than 30
pound-force (133 newtons), more preferably not more than 20 pound-force
(89 newtons), is required.

[0069] FIG. 2 illustrates static mixer 212 with ten mixing elements 214.
In order to achieve adequate and reproducible mixing of parts (A) and
(B), a sufficient number of mixing elements are included. For certain
embodiments, including any one of the above method, device, kit, and
composition embodiments, preferably the static mixer includes at least 8
mixing elements or at least 10 mixing elements. For certain of these
embodiments, the static mixer includes at least 12 mixing elements. While
more mixing elements may be used, the number is kept to that which is
necessary for adequate and reproducible mixing, so as to prevent
unnecessary back pressure resulting from additional, but unnecessary
mixing elements. Static mixer 212 is also shown with optional curved
dispensing tip 204 and optional closure plug 113, which can function to
close outlet openings (not shown) of reservoirs 105 and 106 of device 100
in FIG. 1 to prevent contact between parts (A) and (B) when not in use.

[0070] In another example of a device described herein, FIGS. 3 (exploded
view in perspective) and 4 (cross-sectional view) illustrate device 300,
also in the form of a double syringe, for mixing and dispensing the
multi-part hardenable dental composition. Syringe body 301 includes
reservoir 305, containing part (A) 350 of the composition, and reservoir
306, containing part (B) 355 of the composition. Mixing tube 302 contains
static mixer 312 with mixing elements 314 and is equipped with outlet
311. Mixing tube 302 is removable and replaceable for multi-dose
applications. When mixing tube 302 is installed on syringe body 301,
locking ramps 319 of mixing tube 302 are retained by locking tabs 315.
Plunger 303 in device 300 is used to force parts (A) 350 and (B) 355
through exit passages 307 and 308 into and through mixing tube 302 with a
relatively low force as described above.

[0071] Additional examples of specific device constructions, which may be
used herein, are described, for example, in U.S. Pat. No. 4,538,920
(Drake) and U.S. Publication No. 2007/016660 A1 (Peuker et al.).

[0072] The multi-part hardenable dental compositions described herein not
only provide a low extrusion force when mixed and dispensed according to
the above methods and in the above described device embodiments, but also
provide sufficient strength for temporarily or permanently cementing a
prosthetic device to a dental structure. For certain embodiments,
including any one of the above method, device, kit, and composition
embodiments, when part (A) is mixed with part (B) and the mixture
hardened, Shear Bond Strength according to Test Method II (described
below) of the resulting hardened cement is greater than 0.2 MPa. For
certain of these embodiments, preferably the Shear Bond Strength is at
least 0.5 MPa. In order to facilitate removal, the hardened cement has a
Shear Bond Strength of less than 2 MPa, preferably not more than 1 MPa.
These bond strength values refer to bond strengths to either dentin or
enamel.

[0073] For certain embodiments, preferably each part of the multi-part
hardenable dental compositions described herein includes a balance of
components for ease of compatiblizing each part with the other during
mixing. Accordingly, for certain embodiments, including any one of the
above embodiments, part A comprises the acid-reactive glass particles,
and a water soluble liquid monomer having at least one ethylenically
unsaturated group per monomer molecule; water; and the adhesion reducing
component; and part B comprises the polyacid; and a liquid monomer having
at least one ethylenically unsaturated group per monomer molecule. For
certain of these embodiments, preferably at least one of the parts of the
multi-part hardenable composition includes a component that provides some
cross linking in the composition when hardened. For certain of these
embodiments, preferably part B further comprises a liquid monomer having
at least two ethylenically unsaturated groups per monomer molecule and
having a viscosity less than or equal to the viscosity of Bis-GMA
(2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane, CAS No.
1565-94-2,
[H2C═CH(CH3)CO2CH2CH(OH)CH2OC6H.sub.4-4-
-]2C(CH3)2). For certain of these embodiments, the liquid
monomer has a viscosity of at most 50 percent of the viscosity of
Bis-GMA.

[0074] Each part of the multi-part hardenable dental compositions
described herein has a viscosity which is balanced with respect to the
other parts of the composition. For certain embodiments, preferably the
viscosity of each part is less than 20 fold higher or lower than that of
any other part of the composition. For certain embodiments, including any
one of the above embodiments, part (A) and part (B) each independently
have a viscosity not less than 6 pascal-second (Pas) and not greater than
100 Pas. For certain of these embodiments, the ratio of part (B) to part
(A) viscosity is 1:0.06 to 1:13. For certain of these embodiments,
preferably the ratio of part (B) to part (A) viscosity is 1:0.6 to 1:3.5,
more preferably 1:0.9 to 1:1.6.

[0075] It has been found that the viscosity of part (A) can be controlled
for low extrusion force using coarse particles of the acid-reactive
glass. The coarse particles have an average particle diameter of greater
than about 2 to about 30 micrometers. For certain of these embodiments,
preferably the coarse particles have an average particle diameter of not
more than about 20 micrometers. For certain of these embodiments, the
coarse particles have an average particle diameter of 3 to 10
micrometers.

[0076] In order to achieve good mixing and low extrusion force as
described above and, at the same time, balanced strength properties
(e.g., sufficient strength for desired durability and ease of removal),
for certain embodiments, including any one of the above embodiments, the
acid-reactive glass particles are present in part (A) in an amount of 30
to 70 weight percent. For certain of these embodiments, preferably the
acid-reactive glass particles are present in part (A) at 40 to 60 weight
percent.

[0077] For certain embodiments, including any one of the above
embodiments, part (A) includes water. This provides further control of
the viscosity of part (A) and may further increase compatibility with
other parts of the composition for good mixing. For certain of these
embodiments, the amount of water in part (A) is 5 to 20 percent by weight
based upon the total weight of part (A).

[0078] Nonreactive fillers may also be included in the compositions
described herein to control viscosity as well as for other reasons, such
as to achieve a desired appearance, impart desired strength properties,
impart radiopacity, and the like. For certain embodiments, including any
one of the above embodiments, part (A), part (B), or part (A) and part
(B) further include a nonreactive filler in an amount of 1 to 50 weight
percent based upon the total weight of the part which includes the
nonreactive filler.

[0079] Non-reactive fillers may be selected from one or more of any
material suitable for incorporation in compositions used for medical
applications, such as fillers currently used in dental restorative
compositions and the like. The filler preferably has a maximum particle
diameter less than about 50 micrometers and an average particle diameter
less than about 10 micrometers. When the present compositions are used as
a luting cement, the filler is finely divided and has a maximum particle
diameter less than about 15 micrometers in order to provide a luting
cement with a film thickness in accordance with ISO Standard 3107 of less
than about 25 micrometers. The filler can have a unimodal or polymodal
(e.g., bimodal) particle size distribution. For certain embodiments,
including any one of the above embodiments which includes a nonreactive
filler, the nonreactive filler is selected from the group consisting of
inorganic material, crosslinked organic material, and a combination
thereof. Suitable crosslinked organic materials are insoluble in the
composition, and are optionally filled with inorganic filler. The filler
should be non-toxic and suitable for use in the mouth. The filler can be
radiopaque, radiolucent or non-radiopaque.

[0080] Examples of suitable non-reactive inorganic fillers are
naturally-occurring or synthetic materials such as quartz, nitrides
(e.g., silicon nitride), glasses derived from, for example, Ce, Sb, Sn,
Zr, Sr, Ba and Al, colloidal silica, colloidal zirconia, feldspar,
borosilicate glass, kaolin, talc, titania, and zinc glass; low Mohs
hardness fillers such as those described in U.S. Pat. No. 4,695,251; and
submicron silica particles (e.g., pyrogenic silicas such as the "Aerosil"
Series "OX 50", "130", "150" and "200" silicas sold by Degussa and
"Cab-O-Sil M5" silica sold by Cabot Corp.); metallic powders such as
those disclosed in U.S. Pat. No. 5,084,491, especially those disclosed at
column 2, lines 52-65; and combinations thereof.

[0081] Examples of suitable non-reactive organic filler particles include
filled or unfilled pulverized polycarbonates, polyepoxides, and the like.
Preferred non-reactive filler particles are quartz, submicron silica and
zirconia, and non-vitreous microparticles of the type described in U.S.
Pat. No. 4,503,169. Mixtures of these non-reactive fillers are also
contemplated, as well as combination fillers made from organic and
inorganic materials.

[0082] For certain embodiments, including any one of the above embodiments
which includes a nonreactive filler, preferably the nonreactive filler is
selected from the group consisting of fumed silica, zirconia-silica,
quartz, nonpyrogenic silica, and a combination thereof.

[0083] The surface of the non-reactive filler particles, in certain
embodiments, preferably is treated with a coupling agent in order to
enhance the bond between the filler and polymerizable components when the
composition is hardened. The use of suitable coupling agents include
gamma-methacryloxypropyltrimethoysilane,
gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,
SILQUEST A-1230 (Momentive Performance Chemicals), and the like.

[0084] For certain embodiments, including any one of the above embodiments
which includes a nonreactive filler, part (B) includes the nonreactive
filler in an amount of 5 to 45 weight percent based upon the total weight
of part (B). For certain of these embodiments, preferably the nonreactive
filler is selected from the group consisting of fumed silica,
zirconia-silica, quartz, nonpyrogenic silica, and a combination thereof.
For certain of these embodiments, preferably the nonreactive filler is
silane treated zirconia-silica.

[0085] Part (B) may be in the form of a viscous liquid, a gel, or a paste.
The viscous liquids and the gels typically contain relatively lower
amounts or no nonreactive filler. The pastes typically include relatively
larger amounts of nonreactive filler. For certain embodiments, including
any one of the above embodiments, part (B) is in the form of a paste.

[0086] As indicated above, the multi-part hardenable compositions
described herein include a liquid monomer having at least one
ethylenically unsaturated group per monomer molecule, and in certain
embodiments, preferably such monomers are partially or fully water
soluble. For certain embodiments, preferably ethylenically unsaturated
groups include allyl, vinyl, acrylate, and methacrylate groups. For
certain embodiments, such monomers have a relatively low molecular weight
and include only one ethylenically unsaturated group per monomer
molecule. For certain embodiments, preferably the molecular weight of
such monomers is about 100 to about 1000. For certain embodiments,
including any one of the above embodiments which includes a water soluble
liquid monomer in the multi-part hardenable composition, the monomer is
selected from the group consisting of 2-hydroxyethyl methacrylate,
glycerol monomethacrylate, polyethylene glycol dimethacrylate, sorbitol
methacrylate, and a combination thereof.

[0087] Such monomers have been found to contribute to the ease of
compatibilizing each part with the other during auto mixing and achieving
the desired viscosity described above for parts (A) and (B).

[0088] Suitable water soluble polyacids for part (B) include, but are not
limited to, homo- or copolymers of unsaturated mono-, di-, and
tricarboxylic acids, for example, homo- or copolymers of acrylic acid,
itaconic acid and maleic acid. For certain embodiments, preferably the
water soluble polyacid comprises a polymer having sufficient pendent
ionic groups to undergo a setting reaction in the presence of a reactive
filler and water, and sufficient pendent non-ionically polymerizable
groups to enable the resulting mixture to be cured by a redox curing
mechanism and/or by exposure to radiant energy.

[0089] For certain embodiments, including any one of the above
embodiments, the polyacid is of the Formula I:

B(X)m(Y)n I

[0090] wherein B is an organic backbone, each X independently is an ionic
group which can undergo a setting reaction in the presence of water and
the acid-reactive glass particles, each Y independently is a
non-ionically polymerizable group, m is at least 2, and n is at least 1.
For certain of these embodiments, X is --COOH and Y is an ethylenically
unsaturated group. For certain of these embodiments, preferably the
backbone B is an oligomeric or polymeric backbone of carbon-carbon bonds,
optionally containing non-interfering substituents such as oxygen,
nitrogen or sulfur heteroatoms. The term "non-interfering" refers to
substituents or linking groups that do not unduly interfere with either
the ionic or the non-ionic polymerization reaction. For certain of these
embodiments, preferably B is a hydrocarbon backbone. X and Y groups can
be linked to the backbone B directly or by means of any non-interfering
linking group, such as substituted or unsubstituted alkylene,
alkyleneoxyalkylene, arylene, aryleneoxyalkylene, alkyleneoxyarylene,
arylenealkylene, or alkylenearylene groups. Alkylene and arylene refer to
the divalent forms of alkyl and aryl, respectively. The linking group may
also include linkages such as --OC(═O)--, --C(═O)NH--,
--NH--C(═O)O--, --O--, and the like, and combinations thereof,
wherein each of these may be used in either direction. For certain of
these embodiments, Y is attached to B via an amide linkage. For certain
of these embodiments, preferably Y is an acryloyloxy, methacryloyloxy,
acrylamido, or methacrylamido group.

[0091] The polyacid of Formula I can be prepared according to a variety of
synthetic routes, including, but not limited to, (1) reacting n X groups
of a polymer of the formula B(X)m+n with a suitable compound in
order to form n pendent Y groups, (2) reacting a polymer of the formula
B(X)m at positions other than the X groups with a suitable compound
in order to form n pendent Y groups, (3) reacting a polymer of the
formula B(Y)m+n or B(Y)n, either through Y groups or at other
positions, with a suitable compound in order to form m pendent X groups
and (4) copolymerizing appropriate monomers, e.g., a monomer containing
one or more pendent X groups and a monomer containing one or more pendent
Y groups. The synthetic route (1) above is preferred. Such groups can be
reacted by the use of a "coupling compound", i.e., a compound containing
both a Y group and a reactive group capable of reacting with the polymer
through an X group, thereby covalently linking the Y group to the
backbone B in a pendent fashion. Suitable coupling compounds are organic
compounds, optionally containing non-interfering substituents and/or
non-interfering linking groups between the Y group and the reactive
group.

[0092] Preferred polyacids of Formula I are conveniently prepared by
reacting a polyalkenoic acid (e.g., a polymer of formula B(X)m+n
wherein each X is a carboxyl group) with a coupling compound containing
both an ethylenically unsaturated group and a group capable of reacting
with a carboxylic acid group. The molecular weight of the resultant
ionomers is preferably between about 250 and about 500,000, and more
preferably between about 1,000 and about 100,000. As referred to herein,
"molecular weight" means weight average molecular weight. These polyacids
are selected to be water soluble. Suitable polyalkenoic acids for use in
preparing the polyacids used herein include those homopolymers and
copolymers of unsaturated mono-, di-, and/or tricarboxylic acids commonly
used to prepare glass ionomer cements. Representative polyalkenoic acids
are described, for example, in U.S. Pat. Nos. 3,655,605; 4,016,124;
4,089,830; 4,143,018; 4,342,677; 4,360,605; and 4,376,835. Preferred
polyalkenoic acids are those prepared by the homopolymerization and
copolymerization of unsaturated aliphatic carboxylic acids, for example
acrylic acid, 2-chloroacrylic acid, 3-chloroacrylic acid, 2-bromoacrylic
acid, 3-bromoacrylic acid, methacrylic acid, itaconic acid, maleic acid,
glutaconic acid, aconitic acid, citraconic acid, mesaconic acid, fumaric
acid and tiglic acid. Suitable monomers that can be copolymerized with
the unsaturated aliphatic carboxylic acids include unsaturated aliphatic
compounds such as acrylamide, acrylonitrile, vinyl chloride, allyl
chloride, vinyl acetate, and 2-hydroxyethyl methacrylate ("HEMA"). Ter-
and higher polymers may be used if desired. For certain embodiments,
preferably the homopolymers and copolymers of acrylic acid are used. The
polyalkenoic acid should be substantially free from unpolymerized
monomers and other undesirable components. For certain embodiments,
preferably the polyalkenoic acids include polyacrylic acids, copolymers
of acrylic and itaconic acids, copolymers of acrylic and maleic acids,
copolymers of methyl vinyl ether and maleic anhydride or maleic acid,
copolymers of ethylene and maleic anhydride or maleic acid, copolymers of
styrene and maleic anhydride or maleic acid, and a combination thereof.

[0093] Polymers of formula B(X)m+n can be prepared by copolymerizing
an appropriate mixture of monomers and/or comonomers. Preferably, such
polymers are prepared by free radical polymerization, e.g., in solution,
in an emulsion, or interfacially. Such polymers can be reacted with
coupling compounds in the presence of appropriate catalysts.

[0094] As indicated above, coupling compounds suitable for preparing
polyacids for use herein include compounds that contain at least one
group capable of reacting with X in order to form a covalent bond, as
well as at least one polymerizable ethylenically unsaturated group. When
X is carboxyl, a number of groups are capable of reacting with X,
including both electrophilic and nucleophilic groups. Examples of such
groups include hydroxyl, amino, isocyanato, halo carboxyl, and oxiranyl.
Examples of suitable coupling compounds include, but are not limited to,
acryloyl chloride, methacryloyl chloride, vinyl azalactone,
allylisocyanate, 2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate,
and 2-isocyanatoethyl methacrylate. Other examples of suitable coupling
compounds include those described in U.S. Pat. Nos. 4,035,321 and
5,814,682, the disclosures of which are hereby incorporated by reference.

[0095] For certain embodiments, including any one of the above
embodiments, the polyacid is selected from the group consisting of the
reaction product of a polymer selected from the group consisting of
polyacrylic acids, copolymers of acrylic and itaconic acids, copolymers
of acrylic and maleic acids, copolymers of methyl vinyl ether and maleic
anhydride or maleic acid, copolymers of ethylene and maleic anhydride or
maleic acid, copolymers of styrene and maleic anhydride or maleic acid,
and a combination thereof with a coupling compound selected from the
group consisting of acryloyl chloride, methacryloyl chloride, vinyl
azalactone, allylisocyanate, 2-hydroxyethyl methacrylate, 2-aminoethyl
methacrylate, and 2-isocyanatoethyl methacrylate.

[0096] For certain embodiment, including any one of the above embodiments
which includes a liquid monomer having at least two ethylenically
unsaturated groups per monomer molecule, the polyacid is insoluble in the
monomer having at least two ethylenically unsaturated groups per monomer
molecule. Insoluble means that less than 3% by weight polyacid dissolves
in the monomer at 25° C. For certain of these embodiments, the
monomer having at least two ethylenically unsaturated groups per monomer
molecule is selected from the group consisting of urethane
dimethacrylate, glycerol dimethacrylate, triethyleneglycol
dimethacrylate, polyethyeneglycol dimethacrylates, and a combination
thereof.

[0097] Suitable acid-reactive glass includes ion-leachable glasses, e.g.,
as described in U.S. Pat. Nos. 3,655,605; 3,814,717; 4,143,018;
4,209,434; 4,360,605 and 4,376,835. For certain embodiments, the
acid-reactive glass is preferably selected from borate glasses, phosphate
glasses and fluoroaluminosilicate glasses. For certain embodiments,
including any one of the above embodiments, preferably the acid-reactive
glass is fluoroaluminosilicate (FAS) glass. Suitable acid-reactive
glasses are also available from a variety of commercial sources familiar
to those skilled in the art. For example, suitable acid-reactive glasses
can be obtained from a number of commercially available glass ionomer
cements, such as "GC Fuji LC" cement and "Kerr XR" ionomer cement.
Mixtures of acid-reactive glasses can be used if desired.

[0098] The acid-reactive glass particles may also be subjected to a
surface treatment. Suitable surface treatments include acid washing,
treatment with phosphates, treatment with chelating agents such as
tartaric acid, treatment with a silane or silanol coupling agent. For
certain embodiments, preferably the acid-reactive glass particles are
silanol treated fluoroaluminosilicate glass particles, as described in
U.S. Pat. No. 55,332,429, the disclosure of which is incorporated herein
by reference.

[0099] When mixing the parts of the multi-part composition, it has been
found that better mixing occurs when the parts are in a volume ratio
approaching or at about 1:1, as compared with using relatively larger
differences in the volumes. This results in better properties of the
composition when hardened, for example, higher shear bond strength and/or
diametral tensile strength (DTS). Moreover, mixing parts in volumes that
are very different from each other increases the possibility of
introducing error into the amounts of the components, which would
adversely affect properties. Accordingly, for certain embodiments,
including any one of the above embodiments, the part (A) and the part (B)
are in a volume ratio of 1.2:1 to 1:1.2.

[0100] As indicated above, an extrusion force of less than 40 pound-force
(178 newtons) according to Test Method I applied to the plunger for
extruding the present composition through the static mixer can now be
carried out without the aid of a mechanical advantage provided by an
attached or external device. Extrusion forces considerably lower than 178
newtons have now been achieved. For certain embodiments, including any
one of the above embodiments, the force is less than 30 pound-force (133
newtons). For certain of these embodiments, the force is less than 20
pound-force (89 newtons), preferably less than 15 pound-force (67
newtons). For certain of these embodiments, the force is 10 to 15
pound-force (44 to 67 newtons). It is noted that stiction can make
dispensing the composition with an even lower extrusion force, such as an
extrusion force of 5 pound-force or less, undesirable. This is because
the plunger may momentarily stick, and overcoming this stiction may
require less force than that required to dispense the composition,
resulting in an uncontrolled amount of composition being dispensed.

[0101] As indicated above, the multi-part hardenable dental compositions
described herein include one or more adhesion reducing components. The
adhesion reducing component comprises one or more materials that are
present in sufficient quantity to provide a temporary cement when the
composition is hardened such that the cement has a shear bond strength of
less than 2.0 MPa. Adhesion reducing components include, but are not
limited to, salts or bases to partially neutralize the polyacid, non-acid
reactive materials to reduce the proportion of acid-reactive species in
the composition, and substitution of some or all of the polyacid with a
polyacid of lower molecular weight. The adhesion reducing component may
be added to one or more of the parts of the multi-part compositions and
may be added in such amount as to provide a cement when the composition
is hardened having a shear bond strength in the range desired for its
intended purpose. Mixtures of the adhesion reducing components may be
utilized.

[0102] Suitable salts or bases that can be used to partially neutralize
the polyacid of the composition generally include salts or bases wherein
the pKa of the conjugate acid of the salt is greater than the pKa of the
polyacid. Preferred salts and bases are sodium citrate, potassium
phosphate, monoammonium phosphate, sodium hydroxide, potassium hydroxide,
lithium, sodium or potassium salts, magnesium oxide, sodium oleate,
hydrated or non-hydrated sodium phosphates and hydrated or non-hydrated
potassium phosphates. Typically, the salt or base will be present in
about 0.001 to about 10 weight %, preferably from about 0.5 to about 5
weight %, based on the total weight of the cement composition.

[0103] Suitable non-acid reactive materials include any or all of the
non-reactive fillers mentioned above, either alone or in combination.
Suitable non-acid reactive materials also include chelating agents such
as tartaric acid. Suitable non-acid reactive materials further include
water, polyhydric alcohols such as glycerol, poly(ethylene glycol) and
polypropylene glycol), poly(vinyl acetate) and non-acid reactive
monomers, polymers and oligomers, e.g., polyethylene glycol
dimethacrylate, glycerol dimethacrylate, Bis-GMA, triethylene glycol
dimethacrylate, 2-hydroxyethyl methacrylate, polypropylene glycol
dimethacrylate, urethane dimethacrylate and other non-acid reactive
resins suitable for incorporation into conventional dental materials. The
non-acid reactive material is present in the multi-part hardenable
composition in an amount of 1 to 95 weight %, preferably from 10 to 80
weight %, based on the total weight of the cement composition.

[0104] For certain embodiments, including any one of the above
embodiments, preferably the adhesion reducing component is a non-acid
reactive material selected from the group consisting of zirconia:silica
microparticles, submicron silica, water, glycerol, poly(ethylene glycol),
polyethylene glycol dimethacrylate, triethylene glycol dimethacrylate,
2-hydroxyethyl methacrylate, water soluble or dispersible celluloses, and
a combination thereof. For certain of these embodiments, the adhesion
reducing component is selected from the group consisting of polyethylene
glycol, glycerol, water soluble or dispersible celluloses, and a
combination thereof.

[0105] Substitution of some or all of the polyacid with a polyacid of
lower molecular weight may alternatively or additionally be utilized to
provide a composition, which when hardened is a temporary cement with
sufficiently low shear bond adhesion. For example, a polyacid, e.g.,
polyacrylic acid, with a molecular weight of 2,000 may be used instead of
a polyacid having a molecular weight of 25,000 to 40,000. Polyacids
available commercially include those sold by Aldrich Chemical Co., Inc.
with molecular weights of 2,000, 5,000, 90,000 and 250,000 and
polyacrylic acid sold under the tradename "GOODRITE" (from BFGoodrich
Co., Specialty Polymers & Chemicals Division, Cleveland, Ohio) and
available in molecular weights ranging from 2,000 to 240,000. The lower
molecular weight polyacids generally have a lower solids content. When
desiring to formulate a paste incorporating these lower molecular weight
polyacids, the polyacids can be concentrated without undesirable
gellation to achieve a solids content equivalent to or higher than a
commercially available higher molecular weight polyacid. Typically, the
polyacid of lower molecular weight will be present in about 2 to about 40
weight %, preferably from about 3 to about 20 weight %, based on the
total weight of the composition.

[0106] The multi-part hardenable dental composition used in the
embodiments described herein include at least one component for
initiating polymerization of the monomers in the composition and thereby
further harden and strengthen the composition to a level greater than
that provided by the ionic setting reaction, which occurs between the
acid-reactive glass particles and the polyacid. For certain embodiments,
including any one of the above embodiments, the multi-part hardenable
dental composition can undergo hardening by heat or light activated
polymerization or redox polymerization. For certain of these embodiments,
the multi-part hardenable dental composition can undergo hardening by
photopolymerization or redox polymerization.

[0107] Redox polymerization is provided by separately incorporating an
oxidizing agent and a reducing agent as a redox catalyst system into the
dental composition for curing via a redox reaction. Various redox systems
and their use in ionomer cements are described in U.S. Pat. No.
5,154,762, the disclosure of which is incorporated herein by reference. A
metal complexed ascorbic acid is a preferred reducing agent that provides
cure with excellent color stability. This reducing agent and redox system
is more fully described in U.S. Pat. No. 5,501,727, the disclosure of
which is incorporated herein by reference. The oxidizing agent should
react with or otherwise cooperate with the reducing agent to produce free
radicals capable of initiating polymerization of the ethylenically
unsaturated groups. The preferred amount for each of the reducing agent
and the oxidizing agent is about 0.01 to about 10%, more preferably about
0.02 to about 5%, based on the total weight (including water) of the
unset composition.

[0108] The oxidizing agent and the reducing agent preferably are
sufficiently shelf stable and free of undesirable coloration to permit
their storage and use under typical dental conditions. The oxidizing
agent and the reducing agent are sufficiently soluble and present in an
amount sufficient to permit an adequate free radical reaction rate. This
can be evaluated by combining all of the ingredients of the cement except
for the filler under safelight conditions and observing whether or not a
hardened mass is obtained.

[0109] Suitable oxidizing agents include persulfates such as sodium,
potassium, ammonium and alkyl ammonium persulfates, benzoyl peroxide,
hydroperoxides such as cumene hydroperoxide, tert-butyl hydroperoxide,
tert-amyl hydroperoxide and 2,5-dihydroperoxy-2,5-dimethylhexane, salts
of cobalt (III) and iron (III), hydroxylamine, perboric acid and its
salts, salts of a permanganate anion, and combinations thereof. Hydrogen
peroxide can also be used, although it may, in some instances, interfere
with the photoinitiator, if one is present. The oxidizing agent may
optionally be provided in an encapsulated form as described in U.S. Pat.
No. 5,154,762.

[0110] Reducing agents include ascorbic acid, metal complexed ascorbic
acid, aromatic amines such as dimethylaminophenethanol and
dihydroxyethyl-p-toludine, cobalt (II) chloride, ferrous chloride,
ferrous sulfate, hydrazine, hydroxylamine, oxalic acid, thiourea, alkyl
thioureas and salts of a dithionite, 1-allyl-2-thiourea, thiosulfate,
aromatic sulfinic acid salts such as benzene sulfinic salts and
p-toluenesulfinic salts, sulfite anion and a combination thereof.
Ascorbic acid and aromatic tertiary amines are preferred reducing agents.
For certain embodiments, a secondary ionic salt may be used to enhance
stability of the system, such as described in U.S. Pat. No. 6,982,288.

[0111] The ionomer cement systems of the invention may optionally contain
one or more suitable initiators that act as a source of free radicals
when activated by heat or light. Such initiators can be used alone or in
combination with one or more accelerators and/or sensitizers. The
initiator should be capable of promoting free radical polymerization
and/or crosslinking of the ethylenically unsaturated moiety on exposure
to light of a suitable wavelength and intensity. The initiator preferably
is also sufficiently shelf stable and free of undesirable coloration to
permit its storage and use under typical dental conditions. Visible light
photoinitiators are preferred. The photoinitiator preferably is partially
or fully soluble in the combined liquid components of the composition
parts (A and B).

[0112] Free radical-generating photoinitiators may be used alone, but in
certain embodiments, preferably are used in combination with a
photosensitizer and/or an accelerator. Such initiators can generate free
radicals for addition polymerization upon exposure to light energy having
a wavelength between 200 and 800 nanometers.

[0113] Suitable photoinitiators (i.e., photoinitiator systems that include
one or more compounds) include binary and ternary photoinitiators. In one
example, a ternary photoinitiator may include an iodonium salt, a
photosensitizer, and an electron donor compound as described in U.S. Pat.
No. 5,545,676 (Palazzotto et al.). Examples of iodonium salts include
diaryl iodonium salts, e.g., diphenyliodonium chloride, diphenyliodonium
hexafluorophosphate, diphenyliodonium tetrafluoroborate, and
tolylcumyliodonium tetrakis(pentafluorophenyl)borate. Examples of
photosensitizers include monoketones and diketones that absorb some light
within a range of about 400 nanometers to 520 nanometers, preferably 450
to 500 nanometers. Preferred are alpha diketones that absorb light within
these ranges. Examples of such photosensitizers include camphoroquinone,
benzil, furil, 3,3,6,6-tetramethylcyclohexanedione, phenanthraquinone,
1-phenyl-1,2-propanedione, and other 1-aryl-1-alkyl-1,2-ethanediones, and
cyclic alpha diketones. Most preferred is camphoroquinone. Preferred
electron donor compounds include substituted amines, e.g., ethyl
dimethylaminobenzoate.

[0114] The photoinitiator, when utilized, should be present in an amount
sufficient to provide the desired rate of polymerization. This amount
will be dependent in part on the light source, the thickness of the layer
to be exposed to radiant energy, and the extinction coefficient of the
photoinitiator. Typically, the photoinitiator components will be present
at a total weight of about 0.01 to about 5%, more preferably from about
0.1 to about 5%, based on the total weight of the composition.

[0115] Additional components, which are suitable for use in the oral
environment, may optionally be used in the multi-part hardenable
compositions described herein. In one example, such components include
solvents, cosolvents (e.g., alcohols) or diluents. In another example,
indicators, dyes, pigments, inhibitors, accelerators, viscosity
modifiers, wetting agents, tartaric acid, chelating agents, surfactants,
buffering agents, stabilizers (including free-radical stabilizers),
submicron silica particles, additives that impart fluorescence and/or
opalescence, modifying agents that prolonged working time, and other
materials that will be apparent to those skilled in the art may be used.
Additionally, medicaments or other therapeutic substances can be
optionally added to the compositions. Examples include whitening agents,
breath fresheners, flavorants, fragrances, anticaries agents (e.g.,
xylitol), fluoride sources, remineralizing agents (e.g., calcium
phosphate compounds), enzymes, anesthetics, clotting agents, acid
neutralizers, chemotherapeutic agents, immune response modifiers,
thixotropes, polyols, anti-inflammatory agents, antimicrobial agents,
antifungal agents, agents for treating xerostomia, desensitizers, and the
like of the type which may be used in dental compositions. Combinations
of any of the above additives may also be used in the compositions
described herein. The selection and amount of any one such additive can
be determined by one of skill in the art according to the desired result.

[0116] Modifying agents which may prolong the time between the beginning
of the setting reaction in a restoration and the time sufficient
hardening has occurred to allow subsequent clinical procedures to be
performed on the surface of the restoration include, e.g., alkanolamines
such as ethanolamine and triethanolamine, and mono-, di-, and tri-sodium
hydrogenphosphates. Modifying agents can be added to either part A or
part B. When used, they are present at a concentration between about 0.1
to 10 percent by weight, based on the total composition weight.

[0118] Free radical stabilizers can be used with a photoinitiator to
prevent premature polymerization or to adjust the working time in free
radically initiated compositions. Suitable examples of free radical
stabilizers include, e.g., butylated hydroxytoluene (BHT) and methyl
ethyl hydroquinone (MEHQ).

[0119] Submicron silica particles may be used to improve the handling
properties. Suitable silica particles include pyrogenic silicas such as
AEROSIL series OX 50, 130, 150, 200, and R-8125, available from Degussa
Corp., and CAB-O-SIL M5 silica available from Cabot Corporation.

[0120] Viscosity modifiers include thickening agents. Suitable thickening
agents include hydroxypropyl cellulose, hydroxymethyl celluose,
carboxymethylcellulose and its various salts such as sodium, and
combinations thereof.

[0121] The methods, devices, and compositions described herein are well
suited for a number of dental applications, such as, for example, a
luting cement used to anchor or hold a prosthetic device (e.g., crown,
bridge, inlay, onlay, post, abutment, veneer, prosthetic tooth, and the
like) in place in the mouth; a restorative or filler material used, for
example, for filling a cavity; a thin film used, for example, as a liner
on dentin and enamel or a sealant or sealing material on enamel; an
orthodontic bracket adhesive; a band cement; and the like. For certain
embodiments, including any one of the above embodiments, the multi-part
hardenable dental composition is selected from the group consisting of a
liner material, a luting material, a restorative material, an endodontic
material, and a sealing material. In one example, a temporary crown is
held in place until a final crown is available, yet the temporary crown
can be readily removed when needed. In another example, a prosthetic
device, such as an abutment or crown, is held in place on an implant
where ease of retrieving and/or maintaining the implant over its life of
service is desired. For certain embodiments, the multi-part hardenable
dental composition is an orthodontic bracket adhesive material or band
cement.

[0122] Objects and advantages of this invention are further illustrated by
the following examples, but the particular materials and amounts thereof
recited in these examples, as well as other conditions and details,
should not be construed to unduly limit this invention.

[0124] Auto mixing was carried out using a MIXPAC syringe (Sulzer
Chemtech, Switzerland) with a medium auto mixing tip. The MIXPAC syringe
is 5 ml syringe with dual barrels (1:1 volume ratio) for multi-dose
applications. The part numbers of the syringe parts and mixing tip were
as follows:

[0125] Extrusion force was tested using an (Instron 1123, Instron Corp.
Canton, Mass.) with a crosshead speed at 100 mm/min on the above
described 5 ml MIXPAC syringe with the medium mixing tip. The MIXPAC
syringe with a medium mixing tip on one end and a plunger inserted in the
other end was inserted into a hole on a sample holder, so the Mixpac was
held steady. As the plunger was pushed into the syringe, the peak force
(extrusion force) required while pushing the plunger a distance of 14 mm
into the syringe was measured in unit of pound-force (lb-f).

Test Method II--Compressive Strength

[0126] Compressive strength was evaluated by first injecting the
auto-mixed cement samples into a glass tube having a 4 mm inner diameter.
The ends of the tube were plugged with silicone plugs. The filled tubes
were subjected to 0.275 MPa pressure for 5 minutes. The samples were then
placed in a chamber at 37 degree C. and 90% relative humidity and allowed
to stand for 1 hour. The cured samples were next placed in 37 degree C.
water for 1 day, and then cut to a length of 7 mm. Compressive strength
was determined according to ISO Standard 7489 using an INSTRON®
universal tester (Instron Corp.) operated at a crosshead speed of 1
mm/min. Results were reported in megapascals (MPa).

Test Method III--Viscosity

[0127] Rheological properties were measured on TA instrument AR G2 at room
temperature with simple shear mood. Viscosities of different pastes at
shear rate 20 s-1 were used for demonstration of balanced
viscosities of different pastes Test Method IV--Crown removal, ease of
cleanup after placement, and remnant cement after crown removal

[0128] Extracted human molar teeth were potted using acrylic material in a
mold and subsequently were prepared using a dental hand-piece by a
consultant dentist. Teeth were cleaned by brass brush and polished by
fine pumice and stored in DI water prior to crown seating. Protemp Plus
System crowns (3M ESPE) were made per manufacturer's instructions and
made against corresponding tooth. After crown preparation, cement was
used per instructions to seat the crowns and the assembly was put in 37 C
oven for the specified clean-up/set time, after which the excess cement
was removed (while the ease of clean-up was noted) by a dental explorer,
and the assembly was put in 37 C DI water for 1 week. At crown removal
session, the dentist used a hemostat to grab on the crown per clinical
conditions, and assessed the ease of crown removal on a scale from 1 to
5, from easy to hard. At the same time, notes were made regarding the
percentage of the cement left on tooth vs retained inside the the crown.
Any removal score of 3 and less, and a remnant cement of 5% or less on
tooth, were deemed acceptable from removal point of view.

Preparation of Pastes

[0129] Paste A was prepared by adding HEMA or PEGDMA, DI water, HPC, ATU,
and DMAPE in a mixing cup, and speed mixing on a Speed Mixer (from
FlackTek Inc, Landrum, S.C.) to form a clear solution. The remaining
components were then added according to the formulation, followed by
speed mixing at 300 rpm for 2 minutes. Paste mixing uniformity was
checked, and, if necessary, mixing was continued at the same rpm until a
uniform paste A was formed.

[0130] Paste B was prepared by adding PEGDMA, BHT, BPO, CPQ, and UDMA into
a mixing cup, and speed mixing to form a clear solution. The remaining
components were then added according to the formulation, followed by
speed mixing at 3000 rpm for 2 minutes. Paste mixing uniformity was
checked, and, if necessary, mixing was continued at the same rpm until a
uniform paste B was formed.

[0131] Except for individual viscosity testing, the pastes were loaded
into the dispensing equipment described above, then extruded through the
automixing tip to provide mixed pastes used for the test methods.